You can navigate to other wiki pages related to the current page by selecting these actions, available through the dropdown lists in the edit bars at the top and/or bottom of each page:

LikePages

LocalSiteMap

Additionally, there are the <<PageList>>, <<FullSearch(...)>>, <<Navigation(...)>>, and <<TableOfContents>> macros, which allow you to automatically generate indices for cohesive parts of a wiki (see HelpOnMacros).